Determination Of Arsenic In Commercial Wine Brands Using Redox Titration

Introduction/Problem

In 2015, California wineries came under scrutiny after wine containing illegal and dangerously high levels of poisonous inorganic arsenic was found, according to a lawsuit filed in Los Angeles. (Schiavone, 2015). These brands were very popular and cheap and there was a total of eighty-three (83) brands under scrutiny. No wineries issued recalls, and no retailers pulled wine from store shelves during the legal tussle. The wineries argued in a March 23, 2016 court hearing, that their labels warn about the dangers of alcohol, which met the law's requirements since there has been no government ruling that the trace levels of arsenic found in wine pose a health risk. A judge agreed that the wine companies have followed all California laws. (Belt & Schiavone, 2016).

There should be a law that states that wine should undergo mandatory testing for heavy metals, especially arsenic. Arsenic is a naturally occurring element widely distributed in the earth's crust. In the environment, arsenic is combined with oxygen, chlorine, and sulfur to form inorganic arsenic compounds. Ingesting very high levels of arsenic can result in death. Exposure to lower levels can cause nausea and vomiting, decreased production of red and white blood cells, abnormal heart rhythm, damage to blood vessels, and a sensation of 'pins and needles' in hands and feet. Ingesting or breathing low levels of inorganic arsenic for a long time can cause a darkening of the skin and the appearance of small 'corns' or 'warts' on the palms, soles, and torso. The Department of Health and Human Services (DHHS) and the EPA have determined that inorganic arsenic is a known human carcinogen. Several studies have shown that ingestion of inorganic arsenic can increase the risk of skin cancer and cancer in the liver, bladder, and lungs. (Agency for Toxic Substances & Disease Registry, 2007)

In wine, one factor why there may be arsenic presence, is that the ingredients in wine, like water, are already high in arsenic. Secondly, arsenic may be added to wine and beer during filtration processes to clarify the liquid and give it a “sparkly” look. Third, the alcohol itself may impair our body’s ability to properly detoxify arsenic, allowing higher levels to remain in our system. (Fox News, 2015) The safe amount of arsenic is 10 ppb.

The methods used to test the wine brands for arsenic were High Pressure Capillary Ion Chromatography and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The suggested method is using Redox Titration to test for arsenic content in the wine. This titration method is cheaper as it relates to equipment and reagents.

Methodology

Preparation of Iodine Solution

Dissolve approximately 25 g of potassium iodide in about 50 mL of water. Add to this 6.5 g of iodine crystals. When the iodine has dissolved completely, dilute the solution to about 500 mL. Do in a 600 mL beaker, not a volumetric flask!

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Preparation of Starch Solution:

Dissolve 1 gram of soluble starch in about 5 mL of cold distilled water. Slowly add the starch suspension to 95 mL of rapidly boiling water. Boil until the solution clears. Cool to room temperature. NOTE: Starch solutions often do not keep. Make it the day you will need it (if you also will need it the following period try to keep it--if it has a mold growth then it must be discarded).

Standardization of the Iodine Solution

Weigh out into 250 mL Erlenmeyer flasks FOUR samples of pure As2O3 of about 0.20 g each. Add 10 mL of 4% NaOH solution. Swirl until all As2O3 has dissolved. (You may warm it to hasten solution, if necessary.) Dilute to 50 mL. Cool to room temperature and add 1:5 HCl until the solution turns pink with methyl red and cool again. Add SOLID sodium bicarbonate in small portions until you are sure that no more will dissolve; then add about 3 g in EXCESS. If the bicarbonate is dissolved before a titration is completed, add more bicarbonate. Add 3 mL of starch solution and titrate with the iodine solution immediately. Continue the titration to the first permanent blue color. Calculate the normality of the iodine solution.

Titration of Unknown Arsenic

Dry the unknown for 1 hour at 105oC. Do not OVERHEAT. Cool it in a desiccator. Weigh out into 250 mL Erlenmeyer flasks four samples of 0.4 to 0.5 g each. Add 10 mL of 4% NaOH solution. It may be necessary to warm it in order to hasten solution. Dilute to 50 mL. Cool to room temperature and add 1:5 HCl until solution turns pink with methyl red. Cool again. Add bicarbonate in small portions until you are sure no more will dissolve; then add about 3 g in excess. If the bicarbonate is dissolved before a titration is completed, add more bicarbonate. Add 3 mL of starch indicator and titrate IMMEDIATELY with the standard iodine solution. Calculate the percentage of As2O3 in the unknown after calculating the molarity of the titrant from the known arsenic titrations. (Sherren, 2001)

Discussion

The researcher would titrate using iodine as a titrant. The researcher would use a buffer to control the reaction of the titration. The researcher would use both acid and base to get the desired pH. The standard and unknown are treated in the same manner. Starch is used as an indicator. The sodium bicarbonate is used to make the acidic As2O3 solution basic. (Sherren, 2001) Iodide is a good reducing agent and reduces the oxidizing agent to which it is titrated. In doing so, iodine molecule is formed which is liberated. The amount of iodine molecule formed is directly proportional to the amount of oxidizing agent (arsenic) reduced.

Based on the calculations obtained, if the value for the concentration of arsenic is more than 10 ppb, the wine contains a potentially lethal amount of arsenic.

Conclusion

In conclusion, arsenic is not a heavy metal to bypass in testing wine. There may be more wine brands with trace amounts of arsenic present. However, if they are not tested consistently, human life will be at stake once the wine is consumed. Redox Titration is a recommended technique, as it is cheaper and more reliable way of testing for arsenic, as well as other heavy metals in wine. The lesson learnt from this case study is that Redox Titration is still relevant is test products. The research has also learnt that some of the products we may be consuming may have impurities that can harm humans and that a more scheduled testing systems need to be established.

References

1. Agency for Toxic Substances & Disease Registry. (2007). Toxic Substances Portal - Arsenic. Retrieved 03 21, 2020, from https://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=19&tid=3
2. Belt, D., & Schiavone, R. (2016). Wines Named In Lawsuit Over Arsenic Levels: Case Dismissed (Update). Retrieved 03 21, 2020, from https://patch.com/maryland/annapolis/full-list-wines-named-lawsuit-over-high-arsenic-levels-0
3. Fox News. (2015). Why is there arsenic in wine anyway? Retrieved 03 21, 2020, from https://www.foxnews.com/food-drink/why-is-there-arsenic-in-wine-anyway
4. Schiavone, R. (2015). Drink Any of These Calif. Wines? They Contain Poisonous Arsenic, Class-Action Suit Alleges. Retrieved 03 21, 2020, from https://patch.com/california/banning-beaumont/drink-any-these-wines-they-contain-poisonous-arsenic-class-action-suit-alleges?utm_source=social&utm_medium=hs&utm_campaign=
5. Sherren, A. (2001). Fundamentals of Analytical Chemistry, 7th Ed. Retrieved 03 21, 2020, from http://atsherren.faculty.noctrl.edu/chm210/HOMEPAGE210.html